FI123586B - Pelletizing plant, processing equipment and method - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a pelletizing plant. The invention further relates to a treatment apparatus for treating the drying air of wood chips or wood chips. The invention also relates to a method for treating the drying air of wood chips or wood chips.

Background of the Invention

Wood pellets are wood-based fuel that can be used in district and district heating plants, house and real estate companies, and heating small and leisure houses. Wood pellets can also be used in heat and power plants 15.

Wood pellets are mainly produced by the by-products of wood processing, such as wood chips or shavings. For example, a cutter chip is a short chip made by a planer. The cutter chips are ground into wood flour 20 for making wood pellets. Wood pellets can also be made from coarser by-products of the wood processing industry. Wood pellets can also be made from wood raw material in the form of chips. The chips are dried and ground with a hammer mill, for example. Wood chips are also obtained from, for example, energy wood, small wood and thinning wood.

25 t? The wood pellet is typically a cylindrical extruder having a diameter of about 6 to 12 mm and a length of about 1 to 3 cm. Their solid shape

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o Stays together because lignin is released from the wood heated by the compression o o binds the pellet ingredients together. Often additional £ 30 foreign binders are needed, and starch may be added as the binder. binders

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The purpose is to influence the strength and durability of wood pellets. m

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Wood pellets are typically manufactured in pelletizing plants. According to one example, the pelletizing plant comprises a feed silo of dried wood chips 35, a conveyor screw which enters the milling into a hammer mill, a cyclone which separates the wood flour, a feed screw which conveys the wood flour 2 from a Chip transfer requires various equipment, such as a fan conveyor or a tube to transfer the chips to the cyclone by air blasting (slurry tube). A pellet conveyor, such as a feed screw, is required for transferring the pellets to e.g. a large bag 5 or a silo. For example, an elevator is used to feed the pellet cooler. Pelletizing plants may also have a dryer for drying the chips and a silo for storing the chips. Some pelleting plants are disclosed in EP-2025738-A1 and WO-2010/136327-A1.

10 Traditional and well-known wood pellet production is largely based on shipment of cutter chips and wood chips from various wood processing plants to the pelletizing plant. Raw material supply is limited and dependent on the operation of the above-mentioned wood processing plants, and the quality and humidity of the raw material varies, making the pelletizing plant process difficult to control.

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Drying of the raw material increases the energy costs of the pelletizing plant, and especially drying of fresh or wet wood chips consumes energy and extends the drying time due to the coarse chips. The chip size is generally 5-30 mm, or 50-100 mm. On the other hand, the raw material cutter chips and wood debris 20 may require the addition of one or more binders to the wood flour. The addition of a binder entails costs and, in addition, the additive, especially starch, generates slag and deposits in the combustion boiler when burning wood pellets.

BRIEF SUMMARY OF THE INVENTION

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It is an object of the present invention to provide solutions to eliminate the aforementioned problems related to the availability of the raw material, o the energy consumption of the pelletizing plant, or the operation of pelletizing plant equipment = 30. This is particularly the case for the production of wood pellets

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associated system and its hardware.

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(£> ^ By using fresh wood as a raw material for wood pellets delivered directly to the pelletizing plant for processing, the availability of raw material 35 and independence from the wood processing industry is assured. These 3 sourcing methods also ensure better control of raw material quality.

By making wood chips from a raw material into a wood pellet raw material 5, it is also possible to reduce energy consumption compared to e.g.

Wood chips are made from fresh wood raw material, such as barked tree trunks such as thinning wood or small wood. The thickness of the wood chips 10 is typically about 1-2 mm. In addition, when using wood chips thinner than wood chips, the energy consumption of drying is significantly lower than that of wood chips and the drying process is also faster.

With raw material handling, wood chip production and pelletising in 15 systems, the most energy efficient and commercially viable way to make wood pellets is achieved. When the system also utilizes the bark of the wood to be cut as fuel, the system is energy efficient. In an integrated system, energy management is efficient. The integrated system can utilize the heat energy released by cooling the wood pellets in the combustion boiler or in the drying of the wood chips, thus reducing external energy consumption.

When the solution is a pelletizing plant and its system with an integrated wood pellet production process, the various equipment of the system can be arranged to operate at the rate required for the production process. This makes the system work efficiently.

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Another embodiment of the disclosed solution is also to improve the quality of the wood pellets o so that the addition of separate binders is completely avoided or significantly reduced.

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00 cu When wood chips are dried, they naturally leave the wood chips

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constituents, in particular volatile organic compounds. At the time of sawdust and cutter shaving, or drying of the chips, these ingredients are not recovered according to the prior art, but are discharged into the open air during normal ventilation or ventilation.

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In the present embodiment, these ingredients are recovered and used as binders for wood pellets. The ingredients used as binders are combined with wood flour, for example in a pelletizing machine. The binder returned to the wood pellet increases the strength and handling resistance of the prepared wood pellet.

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Thus, in the prior art processes, some of the binders present in the wood pellet raw material have been removed, for example by drying air, which has caused problems. Problems include breaking wood pellets during transport and handling in transfer conveyors. The cost has been to add extra binder.

Returning to the wood pellet the binders present in its raw material and leaving the raw material, especially during drying, provides more durable wood pellets and even improves their calorific value.

According to one example, the constituents to be collected as binders are present in warm air, which is used to dry the wood chips and is removed from the drying process. Warm air is separated from wood chips, eg by cyclone. The separated air is cooled and condensed and collected. The condensed liquid contains one or more ingredients used as a binder which is separated from the liquid. The binder is utilized as desired when it is returned to the wood pellet production process. Preferably, said binder is injected into the wood flour in a pelleting machine.

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δ ™ The above recovery can be done in an integrated system,

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o which is described in this specification. Another alternative is that o a treatment system that recovers binders is applied e.g.

g at 30 pelletizing plants using wood chips. The binders are then removed

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warm air, which is collected during the drying of the chips, ou The third option is that the treatment system in question absorbs the binders

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recovered and utilized in another system, δ

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The pelletizing plant of the invention is described in claim 1. The processing apparatus of the invention is described in claim 5. The process of the invention is described in claim 8.

5 Description of the drawings

Figure 1 illustrates a wood pellet production process and system, which is an example pelletizing plant.

Figure 2 illustrates in more detail the part of the production process and system of Figure 1 relating to the recovery of binders and their return to the wood pellet production process.

Figure 3 illustrates an operating principle 15 of a pelletizing machine

Detailed Description of the Invention

Figure 1 shows an example of a system which is a pelletizing plant in which wood chips are made into wood pellet raw material.

The system includes a conveyor 10, e.g., a bookstore, which receives the wood material and dispenses it in appropriate doses to the debarking apparatus 11. The system further comprises, for example, a feed conveyor 12, receiving a dose, such as a single tree trunk, and feeding it to the debarking apparatus 11, e.g. debarking drum. The conveyor 10 separates the tree trunks from the bundle received in the conveyor 10 and carries them

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™ in the transverse direction. The feed conveyor 12 carries the tree trunk to it

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o longitudinally and feed it into or out of the system.

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The wood material passes through the peeling apparatus 11 and at the same time the bark and impurities are released. The bark can be collected and burned in a combustion boiler, whereby

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heat is produced to heat the wood drying air, δ

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The intermediate conveyor 13, e.g., a clam, receives the wood from the peeling apparatus 11, stores the wood and feeds it to the next stage of the system.

6 The intermediate conveyor 13 dispenses the wood to the dispenser 14, i.e. the intermediate conveyor 13 feeds the desired amount of wood trunks to the dispenser 14, e.g., by feeding the wood trunks one by one to the dispenser 14. The wood trunks are moved in their transverse direction.

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Dispenser 14 is a transfer and conveyor device for delivering a desired dose of wood material to a cutting apparatus 16. In this example, Dispenser 14 is a conveyor with grabs that raises a dose of dispenser 14 from a receiving tray 15 and drops it into a feeding pan 17 of cutting equipment 16.

The cutting apparatus 16 is provided with a system for monitoring the amount of wood in the feed pan 17. The dispenser 14 and intermediate conveyor 13, as well as, if necessary, the stripping apparatus 11, are controlled so that the receiving tray 15 always has the desired amount of wood.

According to one example, the cutting apparatus 16 comprises a feed trough 17 into which the wood material is fed, and a working plane below it and a machining device. In the feed pan, the tree trunks are held on top of each other and in the desired direction so that they rest on the working plane and rest against the blade of the working device. The machining device is, for example, a rotary cutter or a course which processes the wood into wood chips.

The working plane and the blade of the processing device move back and forth in the longitudinal direction of the wood trunks 25 and form the wood chips. Alternatively, "the tool blade and the work platform remain stationary, so that the feed tray

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™ 17 moves back and forth in the longitudinal direction of the tree trunks.

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o o From the cutting apparatus 16, the wood chips are transferred, for example, by means of a wood chip conveyor 18 g 30, to a wood chip drying apparatus 19, which is e.g.

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dryer and fed with heated air. The temperature in the tumble dryer is about 200 ° C and the wood chips are also in contact with the friction

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tumble dryer or wood chips, which also detaches the ingredients from the wood chips. The thermal energy required for heating the air is provided in a 35 boiler 20, which burns bark removed from the wood and other wood. If necessary, 7 heat exchangers are used for heating the drying air. In the drying apparatus 19, wood chips evaporate various constituents, such as water and volatile organic compounds such as essential oils and resins, which are affected e.g. drying equipment temperature. These volatile ingredients pass with the warm drying air.

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From the drying apparatus 19, the wood chips are transferred to a separating apparatus 21, e.g., a cyclone, in which the drying air and the wood chips are separated. The transfer is effected by the transfer conveyor 30, utilizing, for example, a piping system operated by suction or blowing (e.g., slurry). The warm drying air contains at least 10 water vapors and volatile constituents. In addition to suction or blowing, mechanical conveyors, such as a screw conveyor, a mat conveyor or a scrap conveyor, can be used as transport conveyors at various locations in the system.

Em. cyclone 21 and subsystem are also shown in Figure 2.

15 The system cyclones function based on the principle known in the art of circulating wood chips and air in a cyclone, whereby gravity shifts heavier wood chips down the cyclone and warm air, along with other light ingredients and dust from the top of the cyclone.

The dried wood chips from the cyclone 21 are conveyed via a transfer conveyor 29 to a grinding apparatus 22, where the wood chips are crushed and formed into fine wood flour, e.g. The wood flour 25 is then fed to a pelletizing machine 23, e.g., a pellet press, to obtain finished wood pellets. Solid shape of wood pellets even after pelleting ^ Stays in size because the heat generated during pelleting releases

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o lignin from the wood flour that binds the ingredients of the pellet together. Heat is generated when the wood flour is pressed through the hole matrix g 30 in the pellet press.

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00 ou Figure 3 shows an example of a pellet press operating principle.

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The pellet press typically has a punch matrix 45 that is planar or annular, and is rolled by one or more press rollers 46 that press wood flour 47 through the punch matrix 45 and form wood pellets 48. On the opposite side of the punch matrix 45, 48. The pellet press punching matrix may be movable with the press roll in place or the punch matrix in position with the press roll moving.

In an alternative embodiment of the disclosed solution, the pelletizing machine 23 is preceded, for example, by a mixer, by means of which, for example, desired ingredients such as binders, liquid, or steam are added to the wood flour. Em.

the ingredients are necessary, for example, to change the composition or moisture content of the wood flour. The mixer may be located e.g. in the transfer conveyor 31 between the refining apparatus 22 and the pelletizing machine 23.

As shown in Figure 1, after the pelletizing machine 23, the wood pellets are transferred, for example, by transfer conveyor 24, to the cooling apparatus 25, where the wood pellets heated during the pelleting process are cooled. The cooling apparatus 25 may have a large number of wood pellets stored. The cooling apparatus 25 is e.g. a chamber in which cooling air is blown. Further, to improve the energy efficiency of the system, it is preferable that the recovered air and other light components, such as wood dust, recovered in the cooling apparatus 25 are conveyed through a transfer conveyor 26 to a combustion boiler 20 for use as combustion air.

Alternatively, the heat released by the cooling apparatus 25 may also be recovered by other means, e.g., heat exchangers, and utilized in the drying apparatus 19 for heating either the drying air or the wood chips 25.

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δ ™ The system further includes a transfer conveyor 27, e.g.

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o chilled wood pellets for storage 28. For example, one or o several silos serve as storage 28. Preferably, the silo has the necessary equipment for dispensing the wood pellets g 30 out of the silo, whereby the wood pellets are moved e.g.

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either for car transport or for bagging. Wood pellets are transported ou mm. in big bags.

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The system shown also has a subsystem, i.e. a processing apparatus, which returns the constituents evaporated from the wood chips during drying. Preferably, the dried wood chips and the warm air used in the drying 9 are separated from each other, and subsequently the constituents of the above-mentioned organic compounds are separated from the warm air and the water vapor contained therein. These ingredients are utilized as binders in wood pellets, whereby they are combined with wood flour. The wood flour and binder 5 are preferably combined in a pelletizing machine.

According to one example, the desired binder, or a combination of several binders, is introduced into a pelletizing machine, where the binder is combined with the wood flour, for example by spraying or spraying. In the case of pellet presses utilizing 10 hole matrices, the binder is injected into the wood flour before being pressed through the hole matrix. Figure 3 illustrates one principle in which the binder is introduced into the wood flour 47 by means of a device 50, e.g. a nozzle.

The binder is introduced into the compression space of the pelleting machine, for example by spraying or spraying. If necessary, some hot water vapor is introduced into the compression space with the binder. The compression space is the space in the pelletizing machine in which the wood flour is pressed through the small holes in the matrix using press rollers. By friction, the lignin melts on the surface of 20 wood pellets and holds the wood pellet together. The temperature of the hole matrix during compression is about 100 ° C.

In an alternative embodiment of the disclosed solution, the binder is mixed with the wood flour in a mixer located between the refining apparatus 22 and 25 of the pelletizing machine 23.

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δ ™ Figure 2 shows in more detail the subsystem of the system of Figure 1, where

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o This is an example of an apparatus for recovering one or more of the ingredients used o as a binder.

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The warm air recovered from the separator apparatus 21 and the water vapor contained therein are led to an air treatment apparatus 41 having devices which e.g. water vapor

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and the other volatile constituents are received and concentrated to a liquid containing one or more constituents. The water vapor also carries 35 other processing ingredients into the treatment plant 41, which are utilized as a binder and combined with the wood flour. The processing apparatus 41 10 utilizes, for example, distillation or cooling. In addition, the treatment apparatus 41 includes devices for separating the various constituents from the liquid, e.g. by means of a separating apparatus, and utilizing the recovered constituent as a binder. The treatment plant 41 includes devices for separating, for example, condensed water and other liquid ingredients, e.g. oils. Separation of the constituents utilizes, for example, differences in density and deposition of water and liquid constituents. The separation device utilizes, for example, a separation vessel such as a separation flask or a separating funnel.

According to one embodiment, the treatment apparatus 41 comprises at least one condenser 42 which condenses water vapor and other constituents into a liquid, which is recovered by means of a collecting conduit 37. For example, the condenser 42 comprises a riser pipe 32 into which warm air is led from the separator apparatus 21, and a jacket 33 surrounding the conduit 32 in which the cooling medium is circulated, preferably cooling water.

The cooling water is obtained from the feed pipe 43.

In the example of Figure 2, the treatment apparatus 41 further comprises a second condenser 34 into which the cooled air is supplied from the first condenser 42. The condenser 34 comprises, for example, a vertical cylindrical chamber 35 and the liquid is collected from the lower part of the chamber 35 by means of a collecting conduit. The cooled air is discharged into the open air from the top of the chamber 35, or from the pipe 32, 25 if the cooler 34 is not used.

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In the example of Figure 2, the processing apparatus 41 further comprises a separating apparatus 38,

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9 wherein the condensed water is separated from the other ingredients; all or some of the ingredients are utilized as binders in wood pellets. The condensed liquid g 30 is passed through a collecting conduit 37 to a separator 38

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in the example, the separating apparatus 38 comprises a separating funnel or separating flask 39, from which condensed water is discharged, e.g. by means of piping 40, and one

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the ingredient or several ingredients together are fed to a pelleting machine, S, for example, by means of piping 44. The binder can also be stored in a container 35 in the treatment apparatus 41, whereupon it is introduced as needed. The binder is combined with the wood flour in a pelleting machine, e.g. by means of the device 50 of Figure 3.

According to an alternative embodiment of the solution, one or more of the ingredients 5 are introduced into a mixer which mixes the ingredient with the wood flour before transferring the wood flour to a pelletizing machine 23.

In an alternative embodiment of the disclosed solution, the pelletizing plant comprises at least a cutting apparatus 16 and a pelleting machine 23 10, and equipment therebetween. In one embodiment, the pelletizing plant also comprises a processing apparatus 41 which returns the binders to the pellet or merely recovers the pellets in question. binders. The binders collected are utilized immediately, later or in another system, such as a pelletizing plant.

The treatment apparatus 41 may also treat the hot air used to heat the chips. The warm air is separated from the chips in the cyclone, which has the same function as cyclone 21. The processing equipment 41 can thus be utilized in a plant which dries chips or wood chips.

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The pelletizing plant and processing equipment described above is controlled and controlled by one or more control units. The control unit applies, for example, one or more programmable logic units or other microprocessor-based control devices having either modular or integrated input and output ports to which sensors and actuators are connected. Logic controls t? actuators in accordance with user-created and stored program data and sensors ™ information. The program contains the necessary instructions to

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o the operation of the pelletizing plant and / or the processing equipment is monitored and controlled, o as in the operation described above, g 30 Q_

The invention is not limited to the examples of £ 3 shown above in the description or figures, but may be applied to the following examples.

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according to the claims, δ c \ j 35

Claims (10)

12 A pelletizing plant comprising at least: a cutting apparatus (16) for processing wood chips from wood; A drying apparatus (19) for drying wood chips by drying air; a separating apparatus (21) for receiving dried wood chips and drying air and separating the wood chips from the drying air; a milling apparatus (22) for milling the separated wood chips into wood flour; a treatment apparatus (41) for receiving the separated drying air and compressing the water vapor and wood chip particles transported with the drying air into a liquid, and separating the water and at least one evaporated ingredient from the liquid; an apparatus (23, 50) for combining said separated ingredient with the ground wood flour for use as a binder for wood pellets; and 15 - a pelletizing machine (23) for producing wood pellets from wood flour. A pelletizing plant according to claim 1, characterized in that said pelleting machine is a pelletizing press which receives wood flour and comprises a device (50) for mixing said ingredient with wood flour. 20 A pelletizing plant according to claim 1 or 2, characterized in that the pelleting plant further comprises: a peeling apparatus (11) for removing bark from the wood material used as the raw material for said wood chips; and 25 - a combustion boiler (20), wherein at least the detached bark is burned and 'energy is provided to heat said drying air. C \ J i CD A pelletizing plant according to any one of claims 1 to 2, characterized in that the pelleting plant further comprises: 30. a boiler (20) producing thermal energy for heating the drying air CL; CO ou - a cooling apparatus (25) which cools the wood pellets arriving from the CD pelletizing machine (23) via cooling air; and - a transfer conveyor (26) for recovering the heated cooling air and the light components contained therein in the cooling apparatus (25) and introducing them into the combustion air in the combustion boiler (20). 13 A treatment apparatus for treating wood chips or wood chips drying air, characterized in that the processing apparatus (41) comprises at least: devices (32) adapted to receive drying air utilized for drying wood chips or wood chips containing water vapor and particles of wood chips or wood chips; devices (34, 42) adapted to condense water vapor and volatile constituents carried with said drying air into a liquid; 10 and devices (38) adapted to separate water and at least one evaporated ingredient from said liquid. The treatment apparatus according to claim 5, characterized in that said treatment apparatus (41) further comprises: at least one cooling apparatus (34, 42) adapted to condense the water vapor and constituents of the volatile organic compounds carried with said drying air into said liquid; and 20. a separating device (38) adapted to separate said condensed water and at least one of the volatile constituents from said liquid. The processing apparatus according to claim 5 or 6, characterized in that said processing apparatus (41) further comprises an apparatus (23, 50) which 'combines the ingredient in question with the wood flour for use as a binder for wood pellets. i CD O 8. A method for treating wood chips or wood chips drying air, g 30 characterized in that the method: CL - receiving drying air utilized for drying wood chips or wood chips containing water vapor and constituents of wood chips CD or wood chips; ° - condensing the water vapor and the 35 volatile constituents carried along with said drying air into a liquid; and 14 separating water and at least one evaporated ingredient from said liquid. The method of claim 8, further comprising: combining said ingredient with wood flour for use as a binder for wood pellets; and making wood pellets from wood flour. Method according to claim 8 or 9, characterized in that the method further comprises: condensing, by cooling, water vapor and constituents of the volatile organic compounds carried with said drying air into a liquid; and 15. separating, by deposition, said condensed water from said liquid and said at least one volatile constituent. 20 CO δ c \ j i CD O o X CC CL CO m c \ j CD δ CVJ 15